Optical properties of multilayered porous-Si formed by current pulse modulation during electrochemical anodization

The optical properties of multilayered porous-Si formed by using electrochemical anodization with a current pulse modulation method were investigated. The photoluminescence intensity was observed to increase dramatically and to be slightly blue-shifted with increasing the period of the porous multilayer. The improvement in the photoluminescence property for multi-stacked porous-Si layers might be attributed to an enhancement of the overall size-effect resulting from the insertion of an interlayer with a high porosity between sandwiched layers with low porosity because these multi-stacked porous-Si layers might provide many luminescence centers in the vertical direction as well as the lateral direction, From the photoluminescence and optical transmittance results for thermally treated porous-Si multilayers, the luminescence from multilayered porous Si is thought to originate from nanocrystallites structured with Si-H and SiH ₂ rather than from interface traps between porous-Si and SiO _x.